The whole point of it is that in a truly random system all known patterns should eventually emerge somewhere within it.
So pi (probably) has this property. There are some joke compression programs around this (they don't really work because it takes up more space to store where something in pi is, than storing the thing itself). But it is funny, to think that pi could theoretically hold every past, present, and future piece of information within those digits after the decimal.
https://github.com/philipl/pifs
https://ntietz.com/blog/why-we-cant-compress-messages-with-pi/
I disagree, because they are not the same thing.
Immutable means read only root.
Atomic means that updates are done in a snapshotted manner somehow. It usually means that if an update fails, your system is not in a half working state, but instead will be reverted to the last working state, and that updates are all or nothing.
I create a btrfs snapshot before updates on my Arch Linux system. This is atomic, but not immutable.*
There is also "image based" which distros like ublue (immutable, atomic) are, but Nixos (also immutable and atomic) are not.
*only really before big updates tbh, but I know some people do configure snapshits before all updates.